GB2239976A

GB2239976A - Method of inspecting pancake tape

Info

Publication number: GB2239976A
Application number: GB9027514A
Authority: GB
Inventors: Masaaki Fukushima
Original assignee: Toshiba Emi Ltd
Current assignee: EMI Records Japan Inc
Priority date: 1989-12-20
Filing date: 1990-12-19
Publication date: 1991-07-17
Anticipated expiration: 2010-12-19
Also published as: GB9027514D0; GB2239976B

Abstract

A method of inspecting a pancake tape during recording by a high speed duplicating apparatus in which information is recorded on the pancake tape, while at the same time the information recorded is reproduced for immediate inspection. A plurality of cassette tapes are defined consecutively on the pancake tape. The first cassette tape is inspected to detect a maximum peak level of the reproduced information which is stored as a reference signal. When each of the cassette tapes following the first cassette tape is recorded with the same information as the first cassette tape, the recorded information is simultaneously reproduced to detect a maximum peak level as a data signal. The data signal is immediately compared with the reference signal from the first cassette tape to detect which is greater in magnitude. If the data signal is smaller than the reference signal, the cassette tape is rejected as a defective tape and the recording apparatus is immediately stopped. The same procedure may be used to inspect successive segments of each cassette tape. <IMAGE>

Description

METHOD OF INSPECTING PANCAKE TAPE BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method of inspecting the recording level of a pancake tape which is recorded by a high speed recording apparatus.

Prior Art n conventional pancake tape is a very long magnetic tape on which the music information from a master tape is recorded. It usually has a length equivalent to about 30 cassette tapes. A plurality of pancake tapes are printed from the master tape at a time by means of the high speed recording apparatus. The printed pancake tapes undergo the inspection and good tapes are cut into individual cassette tapes, which are then packaged as individual music cassette tapes for sale.

When printing the pancake tape from the master tape, dust or dirt may often be deposited on the recording head and can cause the recording level to decrease.

Conventionally, an inspection signal is recorded on the pancake tape about five seconds just before the recording completes and the recorded inspection signal is simultaneously reproduced. The reproduced inspection signal is then compared with a predetermined reference level to decide whether the information is recorded on the pancake tape within a predetermined range of recording level. With this conventional method, the improper recording level of tape is detected, if any, at the very end of the recording operation. It is, therefore, difficult to pinpoint where the recording level started to drop. When improper recording level is detected, the entire length of the pancake tape may have to be wasted.

SUMMARY OF THE INVENTION Qn object of the present invention is to provide a method of inspecting a pancake tape in which information can be recorded on the pancake tape while at the same time the recorded information on the pancake tape is reproduced for immediate inspection Another object of the invention is to provide a method of inspecting a pancake tape where an appropriate measure can be taken quickly when abnormal recording level is detected to thereby save material and time.

In a first embodiment, a pancake is inspected through the following procedure. n recording head is first cleaned before loading the pancake onto a high speed recording apparatus. This allows the first portion of the pancake tape, i.e., a first length enough for one cassette tape, to be recorded normally. This first portion is used as a first cassette tape or reference tape. While the recording operation of the first cassette tape is in progress, the first cassette tape is simultaneously reproduced to detect a maximum peak level of the reproduced information. This maximum peak level is stored as a reference signal.

Likewise, a second length enough for one cassette tape adjacent to the first portion of the pancake is recorded, and is simultaneously reproduced to detect a maximum peak level of the reproduced information as a second data signal.

The second data signal is compared with the reference signal to detect which is greater in magnitude. If the second data signal is smaller than the reference signal, the second cassette tape is rejected as a defective tape. The high speed recording apparatus is immediately stopped to halt printing operation. Conversely, if the second data signal is greater than the reference signal, the second cassette tape is a good tape. If the second cassette tape passes the inspection, the inspection proceeds to the third cassette tape. In this manner, each of consecutive portions equivalent to one cassette tape is recorded and the recorded information is simultaneously reproduced for immediate inspection.

In a second embodiment, a pancake is inspected through the following procedure. The information recorded on a first portion of the pancake tape, equivalent to one cassette tape, is divided into a plurality of consecutive subsections. Each of the subsections is recorded on the pancake tape while at the same time the recorded information is reproduced to detect a maximum peak level. The maximum peak level of each subsection is stored in order as a reference signal into consecutive addresses in a memory.

Likewise, a second length enough for one cassette tape adjacent to the first portion of the pancake tape is divided into a plurality of sections, each of which is recorded while also being reproduced so that a maximum peak in that subsection is compared with the reference signal stored in the memory to find out which is greater in magnitude. In this manner, inspection is carried out one after another for all the subsections of the second cassette tape.

BRIEF DESCRIPTION OF THE PREFERED EMBODIMENTS Features and other objects of the invention will be more apparent from the detailed description of the preferred embodiment with reference to the accompanying drawings in which: Fig. 1 is an example of a circuit used in a first embodiment of a method of inspecting a pancake tape according to the present invention; Fig. 2 is a timing chart illustrating the operation of the circuit in Fig. 1; Fig. 3 is an example of a circuit used in a second embodiment of a method of inspecting a pancake tape according to the present invention; Fig. 4 is a timing chart illustrating the operation of the circuit in Fig. 3; Fig. 5 is a flowchart showing the procedure in the first embodiment; and Figs. 6A-6B show a flowchart of the procedure in the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First embodiment Fig. 1 shows a circuit used in a first embodiment of a method of inspecting a pancake tape according to the present invention. Fig. 1 shows a circuit for one channel of a total of four channels of a stereo music that are recorded on the cassette tape. The information recorded on the pancake tape is reproduced while the pancake tape is undergoing recording operation. The information reproduced from the pancake is applied to an input terminal IN and is directed to an amplifier 1, which amplifies the signal and supplies it to a bandpass filter 2.

The output filter 2 is supplied to an AC-to-DC converter 3 by which the signal is converted into a d-c signal, and the d-c signal is then amplified by an amplifier 4.

The output of the amplifier 4 is supplied to a variable resistor 50 by which the signal is adjusted an appropriate signal level before inputting into one of the input terminal of a comparator 51. The output of a (digital-to-analogy converter 55 is inputted into the other input terminal of the comparator 51. An AND gate 52 converts the output of the comparator 51 into a train of pulses with the aid of clock pulses from a clock 53. The train of pulses is supplied to a counter 54. The D/A converter 55 receives a digital signal from the counter 54 and converts it into an analog signal, which is then supplied to the comparator 51.It should be noted that the comparator 51 compares the output of the D/A converter 55 with the output of the variable resistor ! attenuated by 2-6 U, s rather than with the output of the amplifier 4 The variable resistor 50, comparator 51, AND gate 52, counter 54, and D/A converter 55 form a peak-hold circuit for the reference signal, which is enabled by a 1st output of a counter 72. Likewise, the comparator 56, AND gate 57, counter 58, and D/A converter 59 form a peak-hold circuit for the data signal, which is enabled by a 2nd output of the counter 72. It should be noted that the comparator 56 compares the output of the D/A converter 59 with the output of the amplifier 4.

A comparator 61 compares the output of the D/A converter 55 with the output of the D/A converter 59 to output a signal indicative which of the two signal is greater than the other. When a D type flip flop 62 receives a low level of REC signal depicted by (c) in Fig.

2, it reads in the output of the comparator 61 and holds it.

The output of the D type flip flop 62 and the outputs from the other channels (channel 2-4) are ORed by an OR gate 63, which then outputs a signal to stop the high speed recording apparatus if any one of the inputs thereto is a high level.

The comparator 61, D type flip flop 62, and OR gate 63 form a decision circuit 6. A control circuit 7 controls the peak hold circuit 5 and the decision circuit 6. An AND gate 71 outputs a logical product of the REC signal supplied to the REC terminal and the START signal ((g) in Fig. 2) supplied to the START terminal. The counter 72 counts the output of the AND gate 71 and outputs the 1st output to the AND gate 52 to activate the peak hold circuit for the reference signal and the 2nd output to the AND gate 57 to activate the peak hold circuit for the data signal. n delay circuit 73 causes the output of the AND gate 71 to delay and then supplies the delayed pulse to one of the input terminals of an OR gate 74 to ensure that the counter 58 is reset after the D type flip flop 62 has outputted a decision result.The RESET signal ((h) in Fig. 2) is inputted into the reset terminals of the counters 54 and 52, D type flip flop 62, and counter 58 via the OR gate 74 so as to reset the whole circuit for initialization. The OR gate 63 receives the comparison results from the channels 2-4.

Operation of first embodiment The operation of the circuit in Fig. 1 will now be described with reference to Fig. 2.

The recording head of the high speed recording apparatus is cleaned before loading a pancake ((a) in Fig.

2) into the recording apparatus. When the RESET signal ((h) in Fig. 2) is supplied to both the counter 54 and 0 type flip flop 62 and also to the reset terminal of the counter 58 via the OR 74, so that all the elements in the peak hold circuit 5, the decision circuit 6, and control circuit 7.

Then the START signal ((g) in Fig. 2) and REC signal are applied to the START signal terminal and the REC signal terminal, respectively.

Then, the information reproduced from the first cassette tape, i.e., the first portion of the pancake tape, is applied to the input terminal IN. An operator adjusts the variable resistor 50 to set a proper level of data signal to be supplied to the comparator 51. The comparator 51 compares the output of the variable resistor 50 with the analog output of the D/A converter 55 so as to output a signal if the signal from the variable resistor 50 is greater than the analog signal from the converter 55. The output signal of the comparator 51 is ANDed with the clock pulses from the clock 53 to be converted into pulses, which are then counted by the counter 54. The D/4 converter 55 receives the output of counter 54 and converts it into the analog signal (d-c signal).

While the output of the variable resistor 50 is greater than the analog output from the D/n converter 55, the comparator 51 continues to output a high level so that the counter 54 continues to count up. The output of the D,/R converter 55 increases with increasing output of the counter 54. This means that the output of the variable resistor 50 is compared with a continuously increasing reference signal.

When the output of the variable resistor 50 reaches its local peak level, the analog output of D/n converter 55 reaches its maximum. Thus, the comparator 51 stops outputting a high level and the counter 54 halts its counting operation to hold its count. This allows the D/A converter 55 to hold its analog output (d-c signal).

Thereafter, if the output level of variable resistor 50 exceeds the analog output level from converter 55, then the comparator 51 again outputs a high level so that the counter 54 resumes its counting operation from its previous count and continues to count up till a new higher local peak level of the output of variable resistor is reached. In this manner, the maximum peak level of the first cassette tape is detected.

When the REC signal ((c) in Fig. 2) goes low indicating a cue signal at the end of the first cassette tape, the counter 72 counts up so that the 1st output ((e) in Fig. 2) goes low to close the AND gate 52. This causes the peak hold circuit for the reference signal to halt so that the maximum peak level is held as a reference signal. Since the recording head is cleaned prior to recording, the first cassette tape is obviously a good tape in recording level and is used as a reference tape. The thus determined maximum peak level is used as a reference signal, which is held (for 20 minutes or so) till the high speed recording of the entire pancake tape is completed.

Similarly, the maximum peak level of the information reproduced from the second cassette tape is detected and is then held by the peak hold circuit for the data signal. The maximum peak level is used as a data signal. The comparator 61 compares the data signal with the reference signal to output a low signal indicative of a defective tape as depicted by (d) in Fig. 2 if the data signal is lower than the reference signal. When the recording operation of the second cassette tape has completed, the REC signal goes low to trigger the D type flip flop via the AND gate 75 so that the D type flip flop 62 reads in the output of comparator 61 and latches it at Q output thereof. If the second cassette tape is a defective tape, the light emitting diode 64 emits a light informing the operator of the occurrence of a defective cassette tape.Cassette tapes are regarded as a good tape if the reference signal is lower than the data signal, and as a defective tape if the reference signal is higher than the data signal. It should be noted that the input level to the peak hold circuit for the reference signal is attenuated by the variable resistor 50 by a predetermined level, for example 2-6 d8, while the input level to the peak hold circuit for the data signal is not attenuated at all. As recording operation is carried out for cassette tapes one after another, the dust and dirt may well be deposited to cause the recording level to decrease gradually. However, such a decrease in level is usually regarded as normal. Thus, the reference signal depicted by the dotted line of (b) in Fig. 2 is selected to be 2-6 de lower than the expected level of good tapes.

When the inspection of the final cassette tape of the pancake tape has completed, the recording head is again cleaned before the next pancake tape is inspected. The comparator 61 may be a window- comparator having an upper limit and a lower limit so that cassette tapes after the first tape are rejected if the maximum peak level of that cassette is above the upper limit or below the lower limit Second embodiment In the first embodiment, the maximum peak level over the entire length of the first cassette tape is detected and therefore if the recording level of a portion at the maximum peak level of the reproduced information is normal but is abnormal after the maximum peak level, the defect cannot be detected till the next cassette tape is detected its abnormal maximum peak.Not only this wastes two consecutive cassette tapes but also a long time is required before the defect is detected. In a second embodiment, the entire length of each cassette tape is divided into a plurality of short consecutive subsections and the inspection is carried out for each subsection. Fig. 3 shows a circuit used in a second embodiment of a method of inspecting a pancake tape according to the present invention. The figure shows a circuit for one channel of a total of four channels that are recorded on the cassette tape.

The output of an amplifier 4 is supplied to variable resistor 500 by which the signal is adjusted to a proper level. The output of the variable resistor 500 is inputted into one of the input terminals of a comparator 501. To the other input terminal of the comparator 501 is inputted the output of a D/A converter 505. An AND gate 502 converts the output of the comparator 501 into a train of pulses with the aid of clock pulses from a clock 503. The train of pulses is inputted into a counter 504. The D/C converter 505 receives a digital signal from the counter 504 and converts it into an analog signal, which is then supplied to the other input terminal of the comparator 501.

The variable resistor 500, comparator 501, AND gate 502, counter 504, and DJA converter 505 form a peak-hold circuit for the reference signal, which is enabled by a 1st output of a counter 702. n timer 604 outputs a train of high level signal as depicted by TIMER OUT in Fig. 4, each of which corresponds to the respective subsection of a cassette tape.

The counter 605 receives a signal a. shown in FIg. 4, from a buffer 614 to count up and outputs its count as an address signal to a RAM 606. The peak level in a subsection corresponding to this address is written into the RAM 606.

The RAM 606 is in the write mode when the 1st output of the counter 702 is high and in the read mode when the 1st output is low.

Likewise, the comparator 512, AND gate 507, counter 508, D/A converter 509, and OR gate 511 form a peak-hold circuit for the data signal, which is enabled by a Snd output of the counter 702. This peak-hold circuit operates in much the same way as the peak-hold circuit for the reference signal operates. For the respective subsection, a digital comparator 601 compares the output of the counter 508 with the reference signal read out from the RAM 606 so as to output a high signal to the set terminal of a RS flip flop 608 via an AND gate 607 if the data signal is lower than the reference signal. The output of the RS flip flop 611 serves as an alarm signal and is displayed on an alarm displayer in the form of an LED 612. The output of the RS flip flop 611 is also outputted as a defect indicating signal via an OR gate 613 to external circuits.

Fig. 5 is a flowchart showing the procedure in the first embodiment.

O##ation of second embodiment The operation of a circuit in Fig. 2 will now be described with reference to a time chart in Fig. 4.

(Setting the reference signal) The recording head of the high speed recording apparatus is cleaned before loading a pancake into the recording apparatus. When the recording apparatus is started, the AND gate 701 receives both the REC signal and the START signal. A RESET signal is supplied to the counter 702 via an inverter 703 so as to reset the counter 702 while also being applied directly to the reset terminal of the flip flop 611 to reset the flip flop 611.

The output of the AND gate 701 is directed to the input terminal of the counter 702, which outputs a high signal (WRITE signal) onto its 1st output upon the first rising edge. The output of the AND gate 701 is also supplied to the OR gates 506 and 511 to reset the counters 504 and 508, respectively. The output of the AND gate 701 is also supplied to the counter 605 and timer 604 to reset these circuits. Then, the signal reproduced from the first cassette tape, i.e., a first portion of the pancake tape, is applied to the input terminal IN. A signal a shown in Fig.

4 is supplied to the counter 605 so as to increment the signal operates in a manner similar to the first embodiment so as to detect the maximum peak level for period 1 of the TIMER OUT shown in Fig. 4. At the end of period fll a signal t)l passes through the OR gate 602 and appears as a signal b2 at a CS terminal of the RAM 606 so as to activate the RAM 606. The output of counter 504 is written into address #1 in the RAM 606 specified by the output of the counter 605. Then, a signal b3 is applied to the counter 504 via the OR gate 506 to reset the counter 504. Then, a signal b4 is applied to the counter 508 via the OR gate 511.

Since the counter 508 has been reset by the low level of the AND gate 701, resetting the counter 508 again results in no change in the output of the counter 508. Then, a signal a is again supplied to the counter 605 to increment its output to specifying address #2 of the RAM 605. The peak hold circuit for the reference signal detects the maximum peak level for period #2 of the timer signal. At the end of period *2, the signal bl passes through the OR gate 602 and appears as the signal b2 at the CS terminal of the HAM 606 so as to activate the RAM 606. The output of counter 504 is written into address 2 of the RAM 606 specified by the output of counter 605. Then, the signal b3 is applied to the counter 504 via the OR gate 506 to reset the counter 504. In this manner, the similar operation is carried out for each of the remaining periods #3-#7 one after another so that the maximum peak level for the respective subsections of the first cassette tape is stored in the RAM 606. at the end of the first cassette tape, the REC signal goes low.

When the REC signal goes low F the counter 702 counts up so that the 1st output goes low and the 2nd output goes high.

When the Lst output goes low, the RAM goes into the read mode and the RND gate 502 is closed causing the peak hold circuit for the reference signal to stop. The output of the ND gate 701 is supplied to the OR gate 506 to reset the counter 504 and is also supplied to the counter 605 and timer 604 to reset these circuits.

(Detection of the data signal and Comparison with the reference signal) The 2nd output of the counter 702 is supplied to the AND gate 507 to activate the peak hold circuit for the data signal, and is supplied to the AND gate 607 to open the gate. Then, the information reproduced from the second cassette tape of the pancake tape is applied to the input terminal IN.

A signal a shown in Fig. 4 is supplied to the counter 605 so as to increment the counter output. The counter 605 outputs a signal specifying address &num;1 of the RAM 606. At the end of period &num;1 of the second cassette tape, a signal bl is supplied to a monostable multivibrator 608 to trigger the multivibrator 608. The monostable multivibrator 608 outputs to the NAND gate 603 a high signal having a pulse duration a predetermined length of time wider than that of signal bl. To the other input of the NAND gate 603 is inputted a high signal from the 2nd output of the counter 702. Thus, the NAND gate 603 outputs a low signal which is supplied to the CS terminal of RAM 606 via the OR gate 602 so that the data stored in address #1 is read out.The digital comparator 601 receives the maximum peak level for period VL of the second cassette tape from the counter 508 and the maximum peak level read out from address #1 of the RAM. Then, the signal b3 is applied to the chip enable terminal of the digital comparator 601 to activate the comparator 601, which in turn compares the data signal with the reference signal. After the comparison has completed, a signal b4 is inputted into the counter 508 via the OR gate 511 to reset the counter 508. The peak-hold circuit for data signal performs its peak-searching operation for period #2 just as in period &num;1 so as to detect the maximum peak level. Thereafter, the data signal is compared with the reference signal read out from address #2 so as to inspect the recording level of the second subsection.

(Detection of defective tape) For example, at the end of the period &num;4 of the third cassette tape, the digital comparator 601 is enabled by the signal b3 and compares the reference signal read out from address &num;4 of the RAM 606 with the maximum peak level for period #4 of the third cassette tape. Since the data signal is lower than the reference signal, the comparator 601 outputs a high signal to one of the input terminals of the AND gate 607. The output of AND gate 607 triggers the RS flip flop 611 so that the RS flip flop 611 outputs a high signal to cause the light emitting diode 612 to light up.

The light emitting diode 611 or alarm informs the operator that the third cassette tape has a recording level lower than the reference signal and is a defective tape. As for the period #6, the data signal is higher than the reference signal, and therefore the recording level for this period is normal; the comparator output is low. It should be noted that the output of flip flop 611 goes high and holds after the first defect is detected.

While the second embodiment has been described with respect to the case where the signal reproduced from the pancake tape is inspected for one frequency range thereof, the signal may also be inspected for a plurality of frequency ranges by providing a plurality of bandpass filters 2' and 2" ... etc. as shown in Fig. 3 for each of sub-frequency range for more detailed inspection.

Figs. 6A-6B show a flowchart of the procedure in the second embodiment.

Claims

Claims:

1. A method of inspecting a pancake tape on which information is recorded at predetermined intervals, said intervals defining cassette tapes therebetween comprising steps of: recording the information on the cassette tapes while at the same time immediately reproducing the information recorded on the cassette tapes; detecting a maximum value of the peak level of the reproduced information of a first cassette tape; producing a reference signal on the basis of said maximum value of the peak level of the first cassette tape; detecting a maximum value of the peak level of the reproduced information of each of a second cassette tape onward; producing a data signal on the basis of said maximum value of the peak level of each of the second cassette tape onward;; comparing the data signal with the reference signal to output an alarm signal when said data signal is lower than said reference signal.

2. A method according to Claim 1, wherein said reference signal is set a predetermined level below the first peak level.

3. 4 method of inspecting a pancake tape on which information is recorded at predetermined intervals. said intervals defining cassette tapes therebetween, comprising steps of: recording the information on the cassette tapes while at the same time immediately reproducing the information recorded on the cassette tapes; dividing a first cassette tape into a plurality of subsections and dividing each of a second cassette tape onward into a plurality of subsections that cor#espond to the plurality of subsections of the first cassette tape; detecting a maximum value of the peak level of the reproduced information in each of said subsections of the first cassette tape; producing a reference signal for each of said subsections of said first cassette tape on the basis of said maximum value of the peak level of the first cassette tape; ; storing said reference signal into a memory; detecting a maximum value of the peak level of the reproduced information in each of said subsections of said second cassette tape onward; producing a data signal on the basis of said maximum value of the peak level for each of said subsections of said second cassette tape onward; reading out said reference signal from the memory and comparing the reference signal with the data signal for each of said subsections of said second cassette tape onward to output an alarm signal when said data signal is smaller than said reference signal.

4. A method according to Claim 1, wherein said reference signal is set a predetermined level below said peak level of the information reproduced from each of said subsections of said first cassette tape.